Alterations in lycopene concentration and Z-isomer content in egg yolk of hens fed all-E-isomer-rich and Z-isomer-rich lycopene

Effects of feeding lycopene isomers to laying hens on egg qualities such as lycopene concentration and color of the yolk were investigated. Firstly, to evaluate the dietary transfer of lycopene to egg yolk, (all-E)-lycopene-rich diets (lycopene content, 100, 200, or 300 mg/kg diet) were fed to hens for 21 days. Lycopene in egg yolk could be detected after 4 days or more from the start of feeding, and the lycopene concentration increased according to the feed amount and period. Even though most of the dietary lycopene was the all-E-isomer, more than 65% of lycopene in egg yolk was present as Z-isomers. Thus, the effect of lycopene Z-isomer content in the diet (lycopene content, 200 mg/kg diet; lycopene Z-isomer content, 35.1% or 61.3%) on egg qualities was investigated. As the Z-isomer content increased, the lycopene concentration in the egg yolk increased, for example, when fed a diet rich in Z-isomers (61.3%), the lycopene concentration in the egg yolk was approximately three times higher than when fed the (all-E)-lycopene-rich diet for 21 days. The results indicated that Z-isomers of lycopene had higher bioavailability and/or higher transfer efficiency to the egg yolk than the all-E-isomer.